Industrial truck attachment



June 27, 1961 L. G. BERQUIST ETAL 2,990,074

INDUSTRIAL TRUCK ATTACHMENT Filed Sept. 26. 1956 5 Sheets-Sheet 1 FIG. I

INVENTORS. LEONARD G- BERQUIST WYATT A. MILLIOUS JAMES H. NEWHOUSE .A/ L ATTY. 1

June 27, 1961 G. BERQUIST ETAL 2,990,074

INDUSTRIAL TRUCK ATTACHMENT Filed Sept. 26, 1956 5 Sheets-Sheet 2 FIG. 2

INVENTORS. LEONARD G. BERQUIST WYATT A. MILLIOUS JAMES H. NEWHOUSE VXMMMK/ AT TY.

June 27, 1961 L. G. BERQUIST ETAL 2,990,074

INDUSTRIAL TRUCK ATTACHMENT 5 Sheets-Sheet 3 Filed Sept. 26, 1956 June 27, 1961 L. G. BERQUIST ET AL 2,990,074

INDUSTRIAL TRUCK ATTACHMENT 5 Sheets-Sheet 4 Filed Sept. 26, 1956 FIG. 5

INVENTORS.

lhul l Ill l U UU Qo I Lw T Ff m MN G m ATB WM AJV E A LWJ June 27, 1961 Filed Sept. 26, 1956 L. G. BERQUIST ETAL INDUSTRIAL TRUCK ATTACHMENT 5 Sheets-Sheet 5 lNVENTORS. LEONARD G. BERQUIST WYATT A. MILLIOUS JAMES H. NEWHOUSE ATTY.

United States Patent 2,990,074 INDUSTRIAL TRUCK ATTACHMENT Leonard G. Berquist, Niles, and Wyatt A. Millions and James H. Newhouse, Battle Creek, Mich., assignors, by direct and mesne assignments, to Clark Equipment Company, Buchanan, Mich., a corporation of Michigan Filed Sept. 26, 1956, Ser. No. 612,322 14 Claims. (Cl. 214-620) Our present invention relates generally to industrial trucks, and more particularly is directed to a crane attachment for use with industrial lift trucks.

It is an object of our present invention to provide an improved crane which may be employed in the form of an attachment with industrial lift trucks.

It is another object of our invention to provide a universally movable crane which is adapted for employment with industrial lift trucks and which comprises a forwardly extending telescopical boom means rotatable about a vertical axis, and a vertically movable load engaging means adjacent one end of the boom means and independently rotatable in a horizontal plane.

It is another object of our invention to provide load engaging means as described wherein the boom means may be pivoted about a vertical axis and extended and retracted in any given pivoted position thereof, and wherein the load engaging means may be raised, lowered and/ or rotated at any given pivoted, extended, or retracted position of the boom means, whereby a load engaging means is capable of engaging a load which is located on either side of or directly forwardly of the truck, and which is further positioned in any one of a variety of angular relations to the axis of the truck at any such location.

It is a further object of our invention to provide in a crane, a load engaging means which is movable independently of the crane in vertical and horizontal planes, and means for prohibiting such independent movement in a horizontal plane in a given position thereof.

It is a feature of this invention to provide in a crane an improved means for actuating in a vertical direction a load engaging means which is associated with the crane.

It is a still further feature of our invention to provide in a crane means for holding rigid a normally universally movable load engaging means when the load engaging means is located in a predetermined operative position.

The preferred embodiment of our present invention includes a crane support member which is adapted to be detachably secured to the load supporting carriage of an industrial truck. The crane is mounted for rotary movement about a vertical axis located adjacent the support member, such rotary movement being accomplished by a pair of hydraulic cylinder and piston assemblies located on opposite sides of the crane, each of which is connected to the crane and to the support member. The crane includes fixed and movable boom members, the movable boom member being telescoped within the fixed member and longitudinally actuatable by means of hydraulic cylinder and piston means connected at its one end to the fixed member and at its opposite end to the movable member. Means are provided for minimizing the friction resulting from relative longitudinal movement of the boom members.

Adjacent one end of the movable boom member is a suspended load engaging means which is actuatable in a vertical direction by means of another hydraulic cylinder and piston assembly associated with the movable boom member, said load engaging means being rotatable about a suspension member 360 in a horizontal plane and also pivotable in a vertical plane about the suspension member. A retaining or saddle means is provided to cooperate with the load engaging means when it is Patented June 27, 1961 2 raised with the suspension member to its upper vertical limit relative to the boom members so that the load engaging means may be rigidly held in a fixed position. When in such position said latter means can neither be rotated nor pivoted in horizontal or vertical planes, respectively.

In the operation of our present invention the crane may be raised or lowered as a unit on the lifting mast of an industrial lift truck; the boom member of the crane may be extended or retracted, as well as rotated to either side of the truck, for selectively positioning the load engaging means relative to a load; the load engaging means may be rotated in either horizontal or vertical planes, as well as raised or lowered, independently of an extended or rotative position of the movable boom member, and, following engagement with a load, it may be retracted into the retaining or saddle means While the movable boom member is retractedand rotated to a position which is axial of the truck. In the above manner, fully universal movement of load engaging means is provided in three dimensions for maximum versatility in load engaging operations, and retaining means is provided for maintaining the load engaging means in fixed relation to the boom members of the crane under certain operational conditions.

Now, in order to acquaint those skilled in the art with the manner of constructing and using crane mechanism in accordance with the principles of our present invention, we shall describe in connection with the accompanying drawings, a preferred embodiment of our present invention.

In the drawing:

FIGURE 1 is a view in perspective of an industrial lift truck having the crane attachment of our invention illustrated in lowered and normally inoperative position;

FIGURE 2 is a perspective view of the truck shown in FIGURE 1, wherein the crane attachment is shown in an extended and rotated position, and the load engaging means is shown in a lowered and rotated position preparatory to engaging a load;

FIGURE 3 is an enlarged side view of the crane attachment shown in FIGS. 1 and 2;

FIGURE 4 is a plan view of the crane attachment shown in FIG. 3;

FIGURE 5 is an enlarged front view of the crane attachment shown in FIGS. 3 and 4;

FIG. 6 is an enlarged sectional view taken on line 6-6 of FIG. 3; and

FIG. 7 is an enlarged sectional view taken on line 77 of FIG. 3, but with the load engaging means not shown.

Referring now to the drawings, there is indicated generally by the reference numeral 10, an industrial truck having a vertically extending mast construction 12 arranged at the forward end thereof. The truck 10 generally comprises a dirigible wheel 14 adjacent the rear end thereof, and an oppositely disposed pair of dual drive wheels 16 located at the forward end thereof and on the axle housing of which is mounted for pivotal movement the mast '12.

The body of the truck, which is suitably connected to the frame thereof in known manner, is shown generally,

at 18 and includes a cab or operators compartment 20 mounted on the upper portion thereof. The mast construction -12 is connected by means of trusswork 22 to a pair of hydraulic cylinder and piston assemblies 24- which are connected at the one ends thereof to the truck frame, the piston rod ends thereof being connected to the trusswork22 for tilting the mast construction 12 out of a vertical plane in either direction about the drive axle housing.

The mast construction 12 is of well-known construction and comprises generally an outer or fixed channel upright construction 26, an inner or vertically movable channel upright construction 28: mounted in telescoping relation-to thefixedupright '26, andhydraulic cylinder hoistconstruction 30 suitably secured at the lower end portions of plate 36, and by a pair of similarly spaced bracket members 42 located just below respective ones of brackets 40. An upper transverse member 44 of carriage 32 is constructed to provide an opening 46 which corresponds in shape to the outer boundary of bracket members 42 (see broken line at numerals 44 and 46 in FIG. 3) so that the crane attachment may be properly supported on the carriage 32. The lower portion of the support plate 36 may be bolted as at 48 to a transverse member 50 of carriage 32.

The crane assembly 52 primarily comprises a fixed boom assembly 54, a movable boom assembly 56 mounted in telescoping relation to assembly 54, a longitudinally extending hydraulic cylinder and piston assembly 58 fixedly mounted on boom member 54 at the rear end thereof by'means of a pin and yoke connection 60 and at the forward end thereof to the boom member 56 by means of a pin and bracket means 62, an inverted Y-shaped or retaining saddle means 64 connected to the boom assembly 56, a hairpin-shaped hook or load engaging means 66 supported by tension means or chain 68 (which is suitably trained over boom mounted sheaves and connected to the boom member 56 at the upper end thereof), hydraulic cylinder and piston assembly 70 connected by bracket means 72 to the forward end of boom member 56 and to the chain and sheave means, and vertically disposed crane supporting plate means 74 rigidly connected to the under side of boom member 54 and having a rear wardly extending portion 76 which is adapted to receive a vertically extending pivot shaft 78. The crane assembly 52 is rotatably mounted on shaft 78 for rotative movement therewith. Support plate 36 defines an opening 79 in the upper portion thereof which permits the rear end of boom assembly 54 to rotate freely without interferonce.

The shaft 78 is mounted for rotation in a pair-of vertically spaced and forwardly extending bearing members 80 and 82 which are rigidly connected to support plate 36. The lower portion of pivot shaft 78 extends through the bearing 82-and portion 76 of support plate means 74, and the upper portion thereof extends through bearing 80'and a collar 84 to' which collar the shaft is attached by a pin 86, said collar being fixed to a transverse plate 88"of boom assembly 54.

A pair of hydraulic cylinder and-piston assemblies 90 and 92 are disposed on opposite sides of the crane assembly and are connected to upper opposite sides of plate 36 by a pair of yoke and pin means 94 and to opposite sides of boom assembly 54 at the piston rod ends thereof by a pair of bracket and pin means 96.

The fixed boom assembly 54 comprises a pair of laterally spaced f-a'cingchannel members 98 and 100 which are held in fixed and rigid relation to each other by a plurality of longitudinally spaced and generally down wardly facing. C-shaped clamp members 102, 103 and 104. Additional rigidity may be afiorded theboom as sembly 54 by means of a connecting plate member, such as 106, between portions of the upper flanges of channel niembers98 and 100.

The C-clamp 104 is mounted at the forward end of boom assembly 54 by means of pairs of vertically spaced and longitudinally extending bracket members 108 and 110. Attached to the forward surface of C-clamp 104 are a plurality of pairs of upper and lower laterally spaced;

and forwardly extending bracket members 112. Each pair of such bracket members is adapted to receive a stub shaft 11'4 on whichis mounted a roller 116. The members of an additionalpair of such-brackets are located in vertically spaced relation on-eachof the opposite sides of the clamp 104 for receiving elongated shaft and roller members 118 and 120, respectively. A portionof the periphery of each roller 116 is located a predetermined distance inwardly of the inner surface of the-channel member flange adjacent thereto, and a' portion of the periphery of each roller 120 is located a predetermined distance inwardly of the inner surface of the channel" member web adjacent thereto.

The movable boom'assembly 56 com-prises a pair'of laterally spaced facing channel members 122 and 124' which are substantially smaller in cross'section-thanchan-- nels 98 and 100 and which are adapted to betelescopically received within boom assembly 54in inwardly spaced relation to the inner surfaces of channel members 98 and 100. The channel members 122 and124 are maintained in fixedrelatio'n to each other by means of opposite end plate members 126 and 1282 On the rear surface ofconnecting plate 128 (see FIG. 6) are mounted-a pair of vertically spaced, horizontally extending, and rearwardly projecting bracket members 130 and 132 fromwhich upwardly and downwardly project, respectively, pairs of laterally spaced cit-vertical bracket means 134 and 136, respectively.

Mounted in each of the brackets 134 and 136 is a cocked off-vertical roller 138, each of which is adaptedto roll on its periphery on the adjacent inner surface of the flanges of channel members 98 and 100. Mounted on vertically extending stub shafts 140 and 142, which are received by openings in bracket members 130 and 132, are roller members 144, which are adapted to roll on the respective inner surfaces of the webs of channel members 98 and 100. A semi-circular opening is formed in the upper portion of connecting plate 128 so that cylin der means 58 may extend therethrough. The rollers 138 are cooked in such a manner that each is adapted to roll in full surface engagement with the adjacent inner surface of the flange'of channel members 98'and 100; The rollers 144 at the rear end of boom assembly 56 are mounted to cooperate with the rollers 120 which are located'at the for-ward end of said boom assembly such that the webs of the channel members 122 and 124 of said boom assembly are laterally positioned and supported a predetermined distance inwardly of channel members 98and 100. Each of the rearwardly mounted rollers 138 is adapted to cooperate with one of the forwardly mounted rollers 116 so as to support the flange sections of channelmembers 122 and 124 inwardly of the inner surfaces of the flange sections of channel members 98 and 100. It will be noted (FIGS. 5 and 6) that the roll ers mounted on O-clamp 104 abut the outer surfaces of channel members 122 and 124, whereas the rollers mounted on the plate member 128 at the rear end of boom assembly 56 abut the inner surfaces of channel members 98 and 100.

By means of such construction it will be apparent that we have provided a telescoping cnane which is adapted to operate with a high degree of stability and with a minimum amount of friction during relative movement of the boom assemblies 54 and 56. The boom assembly 56 at all times is maintained'in substantially fixed axial alignment with the boom assembly 54 due to the fact that ea'ch of the rollers 116 cooperates with the nearest roller138; and each of the rollers 120 cooperates with the nearest roller 144, to provide a plurality of force couples which resist in both horizontal and vertical planes any force which tends to misalign the movable and fixed boom assembles.

The end of piston rod 148 of hydraulic cylinder and piston assembly 70 is threaded to engage a tapped opening in the center portion of a transversely extending sheave support member 149, the ends of which are of reduced cross-section and are mounted for sliding movement in inwardly opening track means which are formed by longitudinally extending pairs of bars 150 and 151. The pairs of bars 150 and 151 are suitably attached, as by welding, to opposite inner surfaces of the webs of channel members 122 and 124, respectively. The members comprising each pair of bars are vertically spaced to form longitudinally extending track means therebetween along which the sheave support member 149 is actuatable. Mounted on a shaft 152 is a pair of sheaves 156 and 158; the shaft 152 is supported at the opposite ends thereof by a pair of longitudinally extending brackets 159 which may be made integral with the support member 149. Whenever the cylinder assembly 70 is energized to extend piston rod 148, the sheaves 156, 158 and shaft 152 may be actuated longitudinally along the track formed by the said pairs of bars from a maximum forward position to the maximum rearward position thereof as indicated in FIG. 3.

. The inverted Y-shaped saddle means 64 terminates at the upper end thereof in outwardly flared and longitudinally extending portions 160 and 162 (FIG. 7), which portions are suitably attached, as by welding, to the lower flanges of channel members 122 and 124. A transverse stub shaft 164 is mounted between vertical plate portions of the downwardly depending saddle 64 and carries thereon a pair of laterally spaced sheaves 166 and 168. Attached to and extending transversely of downwardly diverging portions of the saddle member 64 are a pair of longitudinally spaced V-shaped members 170 and 172. The legs of member 172 converge at a sharper angle than do the legs of member 178 so that the apex of member 172 is vertically above the apex of member 170. The downwardly diverging portions of the saddle member 64 are provided with a plurality of openings 174 to minimize the Weight thereof. Downwardly depending structural strengthening members 178 and 180 extend transversely of saddle member 64 and are attached, as by welding, to opposite sides thereof.

The load engaging hairpin-shaped hook member 66 is pivotally suspended at the upper leg thereof from a pivot pin 184 which extends between the legs of an inverted U-shaped bracket 186. The bracket 186 is mounted to swivel in a horizontal plane on a pin 188 which depends from the underside of a sheave housing 190. Within housing 190 is suitably mounted a sheave, not shown, which is located in a plane transverse to the planes of the aforementioned double sheaves. An anchor block 192 extends transversely of the boom assembly 56 and is secured at its opposite ends to the webs of channel members 122 and 124. Secured to the anchor block 192 are laterally spaced ends of the chain 68 which extends rearwardly over sheave 156 from its one end connection, thence forwardly over the sheave 166, then downwardly under the sheave housed in member 190, and finally upwardly over sheaves 168 and 158 to its other end connection on anchor block 192. A longitudinally extending shaft or bolt 195 is supported at its opposite ends by members 178 and 180, and functions to guide spaced portions of chain 68 which are disposed on opposite sides of the shaft. The ends of chain 68 are anchored to block 192 by means of a transversely extending pin 193. It will be readily seen that the above described chain and sheave arrangement enables the hook means 66 to be raised or lowered at twice the rate of movement of piston rod 148; this results in a very compact construction in which the length of cylinder and piston assembly 70 tends to be minimized for any given desired vertical traverse of hook means 66.

The various fluid conduits which are connected to the cylinder and piston assemblies 90, 92, 58 and 70 are generally indicated at numeral 198 in FIGS. 1 and 2.. A channel member 200 is suitably secured above and longitudinally of the boom assembly 54 for the purpose of guiding and housing portions of the various conduits which carry pressure fluid to the cylinder assemblies 58 and 70.

In operation, the industrial truck 10' may be maneuvered to the vicinity of a load to be transported from one location to another. Normally, during such movements of the truck, the crane attachment '52 and load hook 66 are positioned as shown in FIG. 1; i.e., the carriage 32 is located in its lowered position on mast structure 12, the crane assembly is positioned axially of the truck by cylinder and piston assemblies and 92, the inner boom assembly 56 is held in a retracted position by cylinder and piston assembly 58, and the load hook 66 is held securely within the apex portions of inverted V- shaped members and 172 of saddle 64.

With the crane assembly 52 and the load hook 66 positioned as shown in FIG. 1, or in any given elevated position thereof on mast structure 12, the truck 10 may be driven forwardly to engage a load, such as a large coil of wire or other material, on the lower leg of hook 66. If it is found necessary to engage a load which is angularly displaced from the center line of the truck, cylinder and piston assemblies 90 and 92 may be energized by operator-control and pump means, not shown, to simultaneously extend one of the piston rods and retract the other, depending on the desired direction of rotation of the crane assembly. If the load is elevated, or if, for example, an obstruction, such as a side of a railroad car, is intermediate the load to be engaged and the crane assembly, the crane may be elevated on mast construction 12 and simultaneously extended and/ or rotated by means of cylinder assembly 58 and/or assemblies 90 and 92, respectively. The piston rod of cylinder assembly 70 may then be retracted from the extended position thereof shown in FIG. 3 to some selected position between full extension and full retraction thereof so as to slacken the chain 68 and permit the hook member 66 to drop vertically to, for example, the position shown in FIG. 2. When the hook is lowered to any position out of saddle 64 it may be pivoted in a vertical plane about pin 184 and may be swivelled a full 360 about pin 188. Such motions of the hook are normally manually controlled by an attendant who assumes a position adjacent the load hook which may be maneuvered as above described to the opposite side of structure intermediate the hook and the truck, such as a stack or pile of material of any description, a wall, or the side of a railroad car.

Once having engaged a load, the hook may be actuated upwardly into the saddle 64 by extension of the piston rod 148 to the position shown in FIG. 3. It will be noted that the inverted V-shaped members 170 and 172 provide downwardly sloping sides which function as cam surfaces, whereby the ends of the upper leg of load hook 66 are automatically guided into the apex of the V-shaped stabilizing members during extension of piston rod 148.

It will be understood that a variety of load engaging means other than the hook 66 may be suspended from a chain or other means adjacent the end of boom assembly 56 for the purpose of engaging various specialized types of loads, and that retaining or saddle means of different design and configuration than that illustrated at numeral 64 may be utilized with any such other load engaging means without departing from the spirit and scope of our invention.

From the above it will be now apparent that we have provided a crane attachment for industrial lift trucks which aifords maximum versatility of motion in operation i.e., the crane assembly is elevatable on and tiltable withzmast structure '12, is rotatable in either direction about the vertical axis of shaft 78, is extendible while the truck is either moving or stationary, andprovides for independent lowering, and raising movements of the load engaging member which may in addition be pivoted and rotated in vertical and horizontal planes,- respectively. It will therefore be seen that loads may be engaged, disengaged, and transported in and to a variety ofrelatively inaccessible locations.

The saddling of the load engaging member under the extendible boom assembly 56--is considered to be an important feature of thisinvention inasmuch as it provides load location rigidity under the crane assembly '52 during transport which avoids swinging movements orpossible loss of load; the saddle also permits disengagement of the load engaging member therefrom with the consequent additional pivotal and rotational movements of the load engaging member afforded thereby.

Now, while we have shown and described what we believe to be a preferred embodiment of our present invention, it will be understood that various modifications and rearrangements may be made therein without departing from the spirit and scope of our present invention.

We claim:

1. In a crane attachment for industrial trucks, at fixed boom assembly, a movable boom assembly telescopical within said fixed boom assembly and means connected to said fixed boom'assembly and to said movable boom assembly for longitudinally extending said movable boom assembly relative to said fixed boom assembly, a downwardly depending saddle means connected to said movable boom assembly intermediate theends thereof, a load engaging means normally nested within said saddle means, and means connected to said movable boom assembly and to said load engaging means fior lowering said load engaging means out of nested relation with said saddle means.

2. In a crane attachment for industrial trucks, a fixed boom assembly, a movable boom assembly telescopical Within said fixed boom assembly and extensible longitudinally thereof, a downwardly depending load stabilizing means connected to said movable boom assembly intermediate the ends thereof, a load engaging means normally nested within said load stabilizing means, and means connected to said movable boom assembly and to said load engaging means for lowering said load engaging means out of nested relation to said load stabilizing means.

3. In a crane attachment for industrial trucks, a fixed boom assembly and a movable boom assembly telescopical within said fixed boom assembly and extensible forwardly thereof, a load stabilizing means depending from said movable boom assembly intermediate the ends thereof, and-a load engaging means depending from said movable boom assembly and normally nested within said load stabilizing means.

4. A crane attachment as claimed in claim 3 wherein said load stabilizing means comprises a saddle-like mem her, and said load engaging means is normally nested within the saddle-like member in such a mannerthat it is held in fixed position relative thereto and'is movable rotationally in at least one plane relative to said saddlelike member when lowered out of nested relationship relative thereto.

5. A crane attachment as clajmed'in claim 3 wherein said operative connection between said load engaging meansand said movable'boom assembly comprises actuatinggmeans connected :to said movable boom assembly and to said'load'engaging means for lowering. said load engaging means out of nested relation to said load stabilining-means.

6. A crane attachment as claimed in claim 4 wherein said? load" engaging means is operatively connected to hydr-aulic cylinder means which is secured at its one end 'adjacent theforward end of the movable boom assembly.

7. ,A crane assembly comprising a forwardly extending boom assembly, load stabilizing means dependingdownwardly from said boom assembly intermediate the ends thereof, a hairpin-shaped load engaging member normally located in nested relationship to said load stabilizir'ig: means such that the load engaging member is held in fixed position relative thereto, sheave means, fluid pressure means connected at its one end to said boom assembly and at its opposite end to said sheave means for actuating said sheave means longitudinally of said boom assembly, a flexible member connected to said boom assembly and to said load engaging member and trained over said sheave means whereby when said fluid pressure means actuates said sheave means in one direction, as aforesaid, said flexible member permits said load engaging means to be lowered out 'of its nested relation to said load stabilizing means, and swivel means connecting said loadengaging member to said flexible member whereby to permit rotation of said load engaging member in a horizontal plane whenever the said member is lowered out of nested relation to said load stabilizing means.

8. A boom assembly comprising a telescopical portion, a downwardly depending inverted Y-shaped saddle means.

connected to the telescopical portion intermediate the ends' thereof, an inverted V-shaped member secured between the diverging portions of said Y-shaped saddle means, and a hairpin-shaped hook member suspended from the telescopical portion and actuatable in a vertical direction within and without said saddle means, said V-shaped member being adapted to receive one leg of said hook member in the apex portion thereof for holding saidhook member in fixed relation to said telescopical portion.

9. A crane assembly comprising a fixed boom means, a movable boom means nested in telescoping relation to said fixed boom means, a downwardly depending saddle means connected to the movable boom means intermediate the cnds thereof, first hydraulic cylinder means connected between said fixed and movable boom means for extensibly actuating said movable boom means relative to said fixed boom means, second hydraulic cylinder means connected to said movable boom means and extensible longitudinally thereof, load engaging means suspended beneath said saddle means, and flexible load elevating means connected to the movable boom means, the second hydraulic cylinder means and the load engaging means such that extension and retraction of said second hydraulic cylinder means eifects vertical movement of said load engaging means within and without said saddle means.

10. A crane assembly as claimed in claim 9 wherein said saddle means comprises a downwardly depending inverted Y-shaped member connected to said movable boom means, and said load engaging means comprises a hairpin-shaped member, one leg of which is receivable in the apex portion of the Y-shaped saddle means.

11. In a crane attachment for industrial trucks, 2. fixed boom assembly and a movable boom assembly telescopical within said fixed boom assembly and extensible forwardly' thereof, said fixed boom assembly comprising a pair of elongated and laterally spaced and facing channel members, means connecting said channel'members for fixing the lateral spacing thereof, said movable boom assembly comprising a second pair of elongated laterally spaced and facing channel members nested within said first pair of channel members, means connecting said second pair of channel members for fixing the lateral spacing thereof, a plurality of roller means connected to said first pair of channel members adjacent one end thereof, 'a plurality of other roller means connected to said second pair of channel members adjacent the opposite end thereof, said first and second plural roller means cooperating to maintain said first and secondchannel means in substantial coaxial relation during telescopical movement of said second pair of channel members, a load stabilizing-means depending from said movable boom assembly intermediate the ends thereof, and'a load engaging means depending from said movable boom assembly and normally nested within said load stabilizing means.

12. A crane attachment as claimed in claim 11 wherein said first plural roller means are rollable on the peripheries thereof along the outer surfaces of said second pair of channel members during telescopical movement thereof, and said second plural roller means are rollable along the peripheries thereof on the inner surfaces of said first pair of channel members, whereby said second pair of channel members are maintained out of frictional relation with said first pair of channel members.

13. A crane assembly as claimed in claim 11 wherein said first and second plural roller means are so constructed and arranged as to provide force couples acting on the webs and flanges of said pair of second channel members which resist lateral and vertical displacement of said second pair of channel members relative to said first pair of channel members.

14. A crane assembly as claimed in claim ll wherein actuating means are provided within the crane assembly for extending said second pair of channel members relative to said first pair of channel members, said actuating means being secured at the one end thereof to said first pair of channel members and at the opposite end thereof to said second pair of channel members.

References Cited in the file of this patent UNITED STATES PATENTS 597,438 Schilling Jan. 18, 1898 678,188 Macbeth July 9, 1901 697,686 Speer Apr. 15, 1902 1,457,450 Morgan June 5, 1923 1,554,551 Biggert et al. Sept. 22, 1925 1,860,733 Fitch May 31, 1932 1,975,094 Fitch Oct. 2, 1934 2,364,493 Ulinski Dec. 5, 1944 2,365,167 Billings Dec. 19, 1944 2,639,048 Glashaw May 19, 1953 2,672,990 Sundin Mar. 23, 1954 2,699,879 Bertram Jan. 18, 1955 2,760,661 Wight et a1 Aug. 28, 1956 2,787,383 Antos et al. Apr. 2, 1957 FOREIGN PATENTS 1,014,666 France June 18, 1952 

